1. Field of the Invention The present invention relates to a ball screw device, and more particularly to a ball screw device including a screw shaft and a ball nut movable relative to each other, and a ball or roller element retaining device attached between the screw shaft and the ball nut for suitably circulating and guiding the ball bearing elements to move through an endless ball guiding passage in the ball screw device or between the two movable members.
2. Description of the Prior Art
Typical motion guide apparatuses, such as the linear motion guide apparatuses comprise two movable members rotatable or movable relative to each other, and a number of ball bearing elements disposed between the two movable members for facilitating the sliding movement between the two movable members, and one or more ball circulating elements attached to the ball nut and communicative with the helical groove portions of the screw shaft and the ball nut for forming an endless ball guiding passage in the ball screw device or between the two movable members and for slidably receiving a number of ball bearing elements.
For example, U.S. Pat. No. 6,652,146 to Lee, U.S. Pat. No. 6,733,179 to Michioka et al., and U.S. Pat. No. 7,044,641 to Scotte et al. disclose three of the typical linear motion guide apparatuses each comprising two movable members movable relative to each other, and a number of ball bearing elements disposed between the two movable members for facilitating the sliding movement between the two movable members, and one or more ball guide devices or circulating elements attached between the two movable members and for slidably receiving a number of ball bearing elements.
For suitably or smoothly guiding or circulating the ball bearing elements through the endless ball circulating channels in the two movable members, the tubular circulating elements or ball guide devices each include a number of spacers coupled together with one or more endless flexible resin connectors for suitably receiving or engaging with the ball bearing elements and for guiding the ball bearing elements to move through the endless ball guiding raceways in and between the two movable members.
However, normally, the ball bearing elements are required to be engaged into the endless flexible coupling members of the ball couplers before the endless flexible coupling members of the ball couplers are fitted and received or engaged into the endless ball guiding raceways in and between the two movable members. For the cited typical linear motion guide apparatuses, the endless flexible coupling members of the ball couplers may be suitably fitted and received or engaged into the endless ball guiding raceways in and between the two movable members.
U.S. Pat. No. 6,481,305 to Nishimura et al., U.S. Pat. No. 6,499,374 to Ohga, and U.S. Pat. No. 7,234,368 to Lin et al. disclose three of the typical ball screw devices each comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and an endless helically running threaded channel or ball guiding raceway provided between the screw shaft and the ball nut for receiving a number of loaded ball bearing elements and for facilitating the sliding movement between the screw shaft and the ball nut, and one or more ball circulating elements attached to the ball nut and communicative with the helical groove portions of the screw shaft and the ball nut for forming the endless helically running threaded channel or ball guiding raceway in the ball screw device or between the screw shaft and the ball nut.
Due to the attachment of the ball circulating elements to the ball nut, the endless flexible coupling members of the ball couplers may not be suitably fitted and received or engaged into the endless ball guiding raceways in and between the screw shaft and the ball nut, such that no flexible coupling members or ball couplers may be used to couple the ball bearing elements together, or the flexible coupling members or ball couplers may not be suitably engaged into the endless ball guiding raceways in and between the screw shaft and the ball nut and also may not be suitably engaged into the ball guiding raceways in the flexible coupling members or the ball couplers.
U.S. Pat. No. 6,089,117 to Ebina et al., U.S. Pat. No. 8,100,025 to Lin, U.S. Patent Application No. US 2008/0000320 to Osterlaenger et al., and U.S. Patent Application No. US 2009/0290819 to Lin disclose several further typical ball screw devices each comprising a ball nut pivotally or rotatably coupled onto a screw shaft, and an endless helically running threaded channel or ball guiding raceway provided between the screw shaft and the ball nut for receiving a number of loaded ball bearing elements and for facilitating the sliding movement between the screw shaft and the ball nut, and one or more ball circulating elements attached to the ball nut and communicative with the helical groove portions of the screw shaft and the ball nut for forming the endless helically running threaded channel or ball guiding raceway in the ball screw device or between the screw shaft and the ball nut.
However, the endless flexible coupling members of the ball couplers also may not be suitably fitted and received or engaged into the endless ball guiding raceways in and between the screw shaft and the ball nut, due to the attachment of the ball circulating elements to the ball nut, such that no flexible coupling members or ball couplers may be used to couple the ball bearing elements together, or the flexible coupling members or ball couplers may not be suitably engaged into the endless ball guiding raceways in and between the screw shaft and the ball nut and also may not be suitably engaged into the ball guiding raceways in the flexible coupling members or the ball couplers.
As also shown in FIG. 7, illustrated is one of the typical ball screw devices comprising one or more ball circulating elements E attached to the ball nut N and communicative with the helical groove portions of the screw shaft S and the ball nut N for forming the endless helically running threaded channel or ball guiding raceway in the ball screw device or between the screw shaft S and the ball nut N.
However, the endless flexible coupling members F of the ball couplers C also may not be suitably fitted and received or engaged into the endless ball guiding raceways in and between the screw shaft S and the ball nut N, due to the attachment of the ball circulating elements E to the ball nut N, and the ball couplers C may be suitably coupled the ball bearing elements B together, or the flexible coupling members F or ball couplers C may not be suitably engaged into the endless ball guiding raceways in and between the screw shaft S and the ball nut N; i.e., the flexible coupling members F of ball couplers C and the ball bearing elements B will be extended out of the ball circulating elements E and thus may not be suitably engaged into the endless ball guiding raceways in and between the screw shaft S and the ball nut N.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional ball screw devices.